This invention relates to ladders. More particularly it relates to ladders with adjustable legs for use on uneven surfaces.
The common ladder is very useful when the legs are resting on a flat surface, however when one attempts to use a ladder with fixed legs on an inclined or uneven surface, it not only is not useful but it becomes a dangerous instrument if one attempts to climb the ladder.
There have been various attempts to provide a ladder with an extendable leg or legs so that the ladder will be level on various inclined surfaces. One such ladder is shown in U.S. Pat. No. 3,882,966 issued to Fasano. The Fasano patent shows an extension device attached to the outside of one of the legs of the ladder. A slidable rail is provided within the Fasano extension and includes a plurality of discrete ratchets which are adapted to engage with a pawl. One of the major drawbacks of the Fasano ladder is that because of these discrete ratchets, the ladder will only be level when the surface upon which it is resting corresponds with a particular ratchet, which of course is an unlikely occurrence.
There are various other teachings of the use of discrete ratchets or holes in an extension device in an attempt to level a ladder. Some of those teachings are shown in the following U.S. patents: U.S. Pat. Nos. 3,948,352, 796,915, 1,177,069, 3,933,222, 1,329,740, 1,862,171, 644,567, 908,387, 2,503,626, and Swiss Patent No. 195584.
U.S. Pat. No. 3,908,796 issued to Hurwitz shows a ladder leveling device which does not utilize ratchets but includes a pair of extension legs which project outwardly from the ladder and which are held in place because of moments of force on each leg which tends to spread the legs apart to cause a frictional engagement. It is not believed that any of the levelers for ladders described above have met with substantial commercial success.